* Lavrov says of deal: "Russia's very close, U.S. is not"
* U.S., Russia in negotiations to end Syria deadlock
* Syrian rebel leader returns to reconcile Islamist fighters
* Russia says ready to help guard Syria chemical arms sites
The United States and China strongly agree on the need for the U.N. Security Council to quickly adopt a binding resolution on eradicating Syria's chemical weapons arsenal, a senior U.S. official said on Thursday in remarks that appeared aimed at putting pressure on Russia to accept the measure.
Russia appeared unswayed. When asked if diplomats were close to a deal on a Syria resolution, Russian Foreign Minister Sergei Lavrov told reporters at the United Nations, "Russia's very close, the U.S. is not."
The United States has been negotiating for days on the sidelines of the U.N. General Assembly with Russia, Syrian President Bashar al-Assad's chief ally, to break a longstanding deadlock on the issue of Syria, where a civil war has raged since 2011.
Western diplomats say a deal with Moscow is close, but Russia dismissed suggestions by Western diplomats on Wednesday that the five permanent Security Council members had agreed on the core of a draft resolution on eliminating Syria's chemical weapons.
U.S. Secretary of State John Kerry met Chinese Foreign Minister Wang Yi for about an hour on the sidelines of the annual gathering of world leaders at the United Nations.
"On Syria, both ministers were in strong agreement on the need for a mandatory and binding U.N. Security Council resolution," said the senior U.S. official, speaking on the condition of anonymity, after the meeting.
"They discussed the value of unity among the P5 (five permanent members of the Security Council) and both felt it is important for the council to act quickly and for OPCW (Organisation for the Prohibition of Chemical Weapons) to similarly act quickly," the official said.
Diplomats from the permanent Security Council members - China, Russia, the United States, France and Britain - have been haggling over the details of a resolution to back an American-Russian accord announced on Sept. 14 in Geneva to eliminate Syria's chemical weapons.
China has backed Russia to veto three council resolutions since October 2011 that would have condemned Assad's government and threatened it with sanctions.
Western diplomats say that Beijing has little reason to support Assad but is eager to ensure Russia will continue to back it in the Security Council on issues like North Korea.
"China follows Russia on Syria," a Western diplomat said on condition of anonymity.
A major sticking point between Russia and Western powers has been whether the resolution is under Chapter 7 of the U.N. charter, which covers the council's authority to enforce its decisions with measures such as sanctions or military force.
Russia has made clear it would not accept an initial resolution under Chapter 7 and that any punitive measures would come only in the event of clearly proven Syrian non-compliance on the basis of a second council resolution under Chapter 7.
The latest draft resolution, seen by Reuters, explicitly states that under Article 25 of the U.N. charter all Security Council decisions are legally binding. The only reference to enforcement in the draft is a threat that if Syria failed to comply with the resolution, the council would impose punitive measures under Chapter 7.
French Foreign Minister Laurent Fabius said that there have been "clear advances" between the five permanent security council members, although details still need to be ironed out.
"A resolution is not in place until it has been adopted and there are still details to be finalized," Fabius told reporters.
Fabius said that he was "satisfied" that at this stage France's demands for the resolution had been accepted by Russia, including a reference to Chapter 7 should Syria fail to comply with its obligations as well as holding accountable those who carried out an Aug. 21 chemical weapons attack.
Assad agreed to destroy Syria's chemical weapons in line with a U.S.-Russian agreement in the wake of that sarin gas strike on civilians in the suburbs of Damascus last month - the world's deadliest chemical arms attack in 25 years.
Washington has blamed Assad's forces for the attack, which it said killed more than 1,400 people, and President Barack Obama threatened a U.S. military strike in response.
Russia and Assad have blamed the attack on rebels battling to overthrow him in a civil war that, according to the United Nations, has left more than 100,000 people dead.
Assad's government last week disclosed to a U.N.-backed weapons watchdog the extent of its arsenal, meeting the first deadline of the ambitious disarmament deal that calls for the weapons to be eliminated by June 2014.
Deputy Foreign Minister Sergei Ryabkov said on Thursday that Russia is ready to help guard Syrian chemical weapons sites and destroy Assad's stockpiles but will not ship any of the chemical arms to Russia for destruction.
Meanwhile, the head of the opposition Syrian Supreme Military Council cut short a visit to France on Thursday and said he would head to Syria for talks with rebel brigades that broke with the Western-backed coalition.
General Salim Idris, who commands the coalition's military wing known as the Free Syrian Army (FSA), said he would travel to Syria on Friday to meet fighters from the 13 groups that rejected on Tuesday the authority of the Turkey-based coalition.
The rebel groups, including at least three considered to be under the FSA umbrella, called on Tuesday for the rebel forces to be reorganized under an Islamic framework and to be run only by groups fighting inside Syria.
The head of the Syrian National Coalition, Ahmed Jarba, will meet with the 14 core members of the "Friends of Syria" group, which is mainly Western and Gulf Arab countries and Turkey at the United Nations later on Thursday. The meeting comes amid increasing tension within the ranks of Syria's opposition.
Thousands of Syrian rebels have broken with the Western-backed coalition and called for a new Islamist front, undermining international efforts to build up a pro-Western military force to replace Assad.